[BUG] .openapi-generator/VERSION always says `unset` on windows (installed via npm)

Bug Report Checklist

• Have you provided a full/minimal spec to reproduce the issue?
• Have you validated the input using an OpenAPI validator (example)?
• What's the version of OpenAPI Generator used? 4.1.2
• Have you search for related issues/PRs?
• What's the actual output vs expected output?

Description

On Windows, when installing openapi-generator via npm (or cloning it), the .openapi-generator/VERSION generated file always says unset instead of the actual version.

openapi-generator version

4.1.2 and master, but present since a while (at least, 4.1.0)

OpenAPI declaration file content or url

Any OpenAPI yml (e.g., modules\openapi-generator\src\test\resources\2_0\petstore.yaml)

Command line used for generation

.\bin\windows\kotlin-client-petstore.bat or .\bin\windows\swift4-petstore.bat

Steps to reproduce

npm install or git clone then run script

Expected output: the generated file .openapi-generator/VERSION should include the proper version number used (currently 4.1.2).

Actual output: the generated file .openapi-generator/VERSION includes unset

NOTE: This works as expected on macOS

Related issues/PRs

N/A

Suggest a fix

Make sure the windows version of the tool can detect its version reliably.

Start by reproducing the issue with npm install or git clone, then run bin/windows/kotlin-client-petstore.bat or bin/windows/swift4-petstore.bat using the referenced petstore.yaml. Trace how the Windows command-line tool determines its version and compare the generated .openapi-generator/VERSION with the expected 4.1.2 value; done means Windows reports the actual version rather than unset.